1. Field of the Invention
The present invention relates to portable electric circular saws equipped with an upper stationary guard and a lower pivoting guard, and more specifically to a tongue attachment for a pivoting lower guard of a portable electric circular saw.
2. Description of the Prior Art
Conventional portable electric power saws include a housing having a motor supported thereon. A shaft driven by the motor has a circular saw blade fixed thereto. A shoe plate is attached to the housing and is adapted to support the saw for movement along a workpiece. A stationary upper guard is fixed to the housing, which provides a protective cover for the upper half of the saw blade. A lower guard is pivotally supported upon the housing and is movable into the upper guard from a first, closed position in which it encompasses substantially the lower half of the saw blade, to a second, retracted position in which a portion of the saw blade edge is exposed and ready to cut into a workpiece. A tension spring or coil spring biases the lower guard toward the closed position. A manipulating handle attached to the housing is situated upwardly from the upper guard at a side thereof and includes a trigger switch to switch the motor on and off. See, for example, Utz U.S. Pat. No. 2,737,985.
Conventionally, the upper guard on portable electric circular saws comprises an interior wall integral with or attached to the housing; an annular, exterior wall parallel to the interior wall; and a peripheral wall in the form of a semicircular band that joins the exterior and interior walls. The lower guard includes an interior wall having an integral, centrally-disposed, apertured hub for pivotally mounting the lower guard on a collar disposed about the motor shaft and attached to the housing; an annular, exterior wall parallel to the interior wall; and a semicircular band-shaped peripheral wall that joins the exterior and interior walls. The peripheral wall of the upper guard is wider than the peripheral wall of the lower guard, which permits the lower guard to telescope into the upper guard. A forwardmost portion of the lower guard conventionally is adapted to present a bearing surface to a nearest edge of a workpiece that will cause the lower guard to progressively move from a closed position to a retracted position as the saw is initially fed forward into the workpiece--that is, the leading edges of the interior and exterior walls of the lower guard move into sliding engagement with a nearest edge of the workpiece. Conventionally, the leading edge of the interior wall of the lower guard follows a quarter-circular arc, more or less, directed radially inward toward the rotational axis of the saw, which arc typically is chosen to be about half of the radius of curvature of the peripheral wall of the lower guard--that is, about half of the radius of the largest circular blade that the saw will accommodate. Thus, even as the lower guard moves from a closed position to a retracted position as the saw is fed into a workpiece, the direction of feed of the saw remains normal to the portion of the leading edge of the interior wall of the lower guard that engages the workpiece. The leading edge of the exterior wall, however, although usually also curved radially inward, is conventionally of diminished radius of curvature as compared to the leading edge of the interior wall of the lower guard. When attempting to saw through relatively thin wood, such as plywood, however, the leading edge of the exterior wall in such conventional saws tends to bind or snag on the nearest edge of the cut, bifurcated workpiece, thereby impeding forward feed of the saw into the workpiece, particularly when the bifurcated portions of the workpiece become misaligned. The present invention is intended to prevent such binding and snagging of the lower guard.